1. Technical Field
The present invention is related to a linear vibrator.
2. Description of the Related Art
A linear vibrator is a part that converts electrical energy into mechanical vibrations by using the principle of generating electromagnetic forces, and is commonly installed in a mobile phone to generate a soundless vibrating alert.
With the rapid expansion of mobile phone markets and increased functionalities added to the mobile phone, mobile phone parts are increasingly required to be smaller and better. As a result, there has been an increased demand for the development of a new structure of linear vibrator that can overcome the shortcomings of conventional linear vibrators and effectively improve the quality.
As mobile phones having a bigger LCD screen have become popular for the past few years, there have been an increasing number of mobile phones adopting a touch-screen method, by which vibration is generated when the screen is touched. Touch screens particularly require that the linear vibrator has a greater durability due to a greater frequency of generating the vibration in response to the touch compared to the vibration bell for incoming calls and that the vibration has a faster response to the touch made on the touch screen, in order to provide a user a greater satisfaction from sensing the vibration when touching the touch screen.
The conventional linear vibrator commonly used in mobile phones generates a rotational force to cause mechanical vibrations by rotating an eccentric (unbalanced) weight. The rotational force is generated by supplying an electric current to the coil of a rotor through point contacts between a brush and a commutator by way of rectifying action.
However, the brush type structure using such commutator has a shorter motor life due to mechanical friction and electrical sparks, which cause wear and black powder, between the brush and the commutator when the motor rotates. Moreover, when voltage is supplied to the motor, it takes time to reach the target magnitude of vibration by the rotational inertia of the motor. Thus, it is difficult to implement the vibration that is appropriate for touch screen phones.
Furthermore, although a linear vibrator uses an electromagnetic force having a predetermined resonant frequency to generate vibrations by use of a spring installed in the vibrator and a mass coupled to the spring, it is difficult to obtain a sufficient magnitude of vibration due to the space limitation because mobile devices in which the linear vibrator is installed become thinner.